Field of the Invention
The invention relates to closing arrangements provided for sliding doors and analogous elements which are adapted to move to a closed position along the lengthwise tracks by a driving force applied to rod-like connecting links engaged to a rotor and having a drag arrangement for limiting the closing speed of the door in its operation.
A conventional closing arrangement known from the German Pat. No. 668,313 involves a device, wherein a closing force applied to the sliding door is transmitted through connecting links to a chain which is connected to the door at one side, and to a winding drum at the other side. In order to restrict the closing speed of the sliding door the chain is placed about a sprocket which during door closing movement is connected through a gear transmission with a bladed rotor. Due to the high transmission ratio of the gear transmission the rotor turns at high speed and slows down the movement of the chain and consequently of the door due to the air drag acting upon the rotor blades.
During the opening movement of the sliding door the rotor does not rotate, because the sprocket actuates a ratchet and a ratchet pawl that prevent transmission of motion to the rotor. In its fully open position, the slidable door is subjected to the action of a mechanical ratchet device which holds the door in its opening position in which the bladed rotor is arrested by a spring-biased locking element. A pendulum is provided in the arrangement to delay disengagement of the locking element from the rotor, so that the sliding door remains in its open position for a predetermined short period of time, whereafter the door automatically returns to closed position which being retarded by the rotor. However, it is disadvantageous in this known closing arrangement that the sliding door can remain open only when it is in its fully open position, and that the period during which it remains open is strictly limited. If the door is required to open only partially, then it must be manually held by an operator, because otherwise it will immediately return to its closed position.